1. Field of the Invention
Embodiments of the present invention generally relate to a method and/or apparatus for deploying wireline tools with a non-electric string.
2. Description of the Related Art
Wellbores are typically formed by drilling a hole into the earth through use of a drill bit disposed at the end of a drill string. Most commonly, the drill string is a series of threaded tubular members, such as steel pipe. Weight is applied to the drill string while the drill bit is rotated. Fluids are then circulated through a bore within the drill string, through the drill bit, and then back up the annulus formed between the drill string and the surrounding wellbore. The circulation of fluid in this manner serves to clear the bottom of the hole of cuttings, serves to cool the bit, and also serves to circulate the cuttings back up to the surface for retrieval and inspection.
With today's wells, it is not unusual for a wellbore to be completed in excess of ten thousand feet. The upper portion of the wellbore is lined with a string of surface casing, while intermediate portions of the wellbore may be lined with liner strings. The lowest portion of the wellbore remains open to the surrounding earth during drilling. As the wellbore is drilled to new depths, the drill string becomes increasingly longer. Because the wells are often non-vertical or deviated, a somewhat tortured path can be formed leading to the bottom of the wellbore where new drilling takes place. Because of the non-linear path through the wellbore, the drill string can become bound or other wise stuck in the wellbore as it moves axially or rotationally. In addition, the process of circulating fluids up the annulus within the earth formation can cause subterranean rock to cave into the bore and encase the drill string. All drilling operations must be stopped and valuable rig time lost while the drill string is retrieved (a.k.a. fished).
Because of the length of the drill string and the difficulty in releasing stuck portions, it is useful to know the point at which one tubular is stuck within another tubular or within a wellbore. The point above the stuck point is known as the “free point.” It is possible to estimate the free point from the surface. This is based upon the principle that the length of the tubular will increase linearly when a tensile force within a given range is applied. The total length of tubular in the wellbore is known to the operator. In addition, various mechanical properties of the tubulars, such as yield strength and thickness, are also known. The operator can then calculate a theoretical extent of tubular elongation when a certain amount of tensile force is applied. The theoretical length is based on the assumption that the applied force is acting on the entire length of the tubular.
The known tensile force is next applied to the tubular. The actual length of elongation of the tubular is then measured at the surface of the well. The actual length of elongation is compared with the total theoretical length of elongation. By comparing the measured elongation to the theoretical elongation, the operator can estimate the sticking point of the tubular. For example, if the measured elongation is fifty percent of the theoretical elongation, then it is estimated that the tubular is stuck at a point that is approximately one half of the length of the tubular from the surface. Such knowledge makes it possible to locate tools or other items above, adjacent, or below the point at which the tubular is expected to be stuck.
It is desirable for the operator to obtain a more precise determination of the stuck point for a string of tubulars. To do this, the operator may employ a tool known as a “free point tool”. The prior art includes a variety of free point tools and methods for ascertaining the point at which a tubular is stuck. One common technique involves the use of a free point tool that has either one or two anchors for attaching to the inner wall of the drill pipe. The tool is lowered down the bore of the drill string with a run-in string, and attached at a point to one of the tubulars. The tool utilizes a pair of relatively movable sensor members to determine if relative movement occurred. The tool is located within the tubular at a point where the stuck point is estimated. The tool is then anchored to the tubular at each end of the free point tool, and a known tensile force (or torsional force) is applied within the string. Typically, the force is applied from the surface.
If the portion of the tubular between the anchored ends of the free point tool is elongated when a tensile force is applied (or twisted when a torsional force is applied), it is known that at least a portion of the free point tool is above the sticking point. If the free point tool does not record any elongation when a tensile force is applied (or twisting when a torsional force is applied), it is known that the free point tool is completely below the sticking point. The free point tool may be incrementally relocated within the drill string, and the one or more anchor members reattached to the drill string. By anchoring the free point tool within the stuck tubular and measuring the response in different locations to a force applied at the surface, the location of the sticking point may be accurately determined.
Typically, the run-in string is wireline. Wireline is a cable having electrically conductive wires through which voltage may be supplied to power and control the tool. The wireline includes one or more conductive wires surrounded by an insulative jacket. The conductive wires supply a voltage signal to the tool from a voltage source at the surface. Typically, an operator at the surface controls the tool by varying the voltage signal supplied to the tool. For example, the operator may apply and remove the voltage signal to cycle power on and off, adjust a level of the voltage signal, or reverse a polarity of the voltage. The tool is designed to respond to these voltage changes in a predetermined manner.
A less expensive, non-electric support cable is commonly referred to as slickline. Because slickline has no conductive lines to supply power to the attached tool, the types of the tools deployed on slickline are typically non-electric tools, such as placement and retrieval tools, mandrels, etc. Recently, battery powered tools have recently been developed for slickline operation. Operation of the battery powered tools may be initiated by lowering a slip ring device down the slickline that comes in contact with a switching device on a top surface of the tools. Alternatively, operation of the tools may be initiated by a triggering device that generates a trigger signal, for example, based upon wellbore pressure (BHP), wellbore temperature (BHT), and tool movement. Regardless of the method of initiation, the absence of electrically conductive wires prevents conventional surface intervention used to control wireline tools, which typically limits tools deployed on slickline to simple tools requiring little or no control, such as logging tools.
Accordingly, a need therefore exists for a free point tool that can be quickly run into a wellbore on a more economical basis.